1. Field of the Invention
The present invention relates generally to a fluid-filled resilient engine mount of a bushing type for damping vibrations by utilizing elasticity of a resilient member and a viscous resistance of a fluid. More particularly, the invention is concerned with an engine mount of such type suitable for flexibly supporting a transverse engine of an FF automobile.
2. Discussion of the Related Art
Various types of resilient or elastic mounts have been proposed for elastically or flexibly supporting an engine of an automotive vehicle on its body. For supporting an engine of FF (front-engine front-drive) vehicles, engine mounts of a cylindrical bushing type have been increasingly used, for their comparatively excellent vibration damping characteristics. A typical example of such a bushing type uses a resilient member interposed between an inner sleeve and an outer sleeve. Since the damping capability of a resilient member itself is limited, various attempts have been recently made to use a fluid-filled resilient engine mount which utilizes a viscous resistance of a fluid flowing through an orifice, to provide a large damping effect for engine-idling and other low-frequency vibrations, and which is adapted to provide relatively low dynamic spring constant for high-frequency vibrations.
An example of such a fluid-filled resilient engine mount is known, which includes an inner sleeve, an outer sleeve located radially outwardly of the inner sleeve and having an axis parallel to an axis of the inner sleeve, and a generally annular resilient member interposed between the inner and outer sleeves. The resilient member has a plurality of voids which are spaced from each other in its circumferential direction and open in its outer surface. The outer sleeve closes the voids and thereby cooperates with the resilient member to define a plurality of fluid chambers filled with a fluid. These fluid chambers are held in communication with each other at least one orifice.
The engine mount of the type indicated above is capable of providing a desirable damping effect by means of a viscous resistance to flows of the fluid through the orifice or orifices. However, this type of engine mount has no satisfactory provisions for protecting the resilient member from an excessive amount of elastic deformation of the resilient member interposed between the inner and outer sleeves. Therefore, repeated radial movements of the inner and outer sleeves relative to each other upon applications of excessively large vibrational loads therebetween will cause the resilient member to have repeated radial elastic deformation in its radial direction, resulting in reducing the durability of the resilient member and consequently shortening its life expectancy. Further, the excessive deformation of the resilient member will deteriorate the fluid tightness of the fluid chambers, i.e., sealing between the outer sleeve and the opening of the voids in the resilient member.